Show
Recommended textbook solutions
Hole's Human Anatomy and Physiology13th EditionDavid N. Shier, Jackie L. Butler, Ricki Lewis 1,402 solutions
Hole's Human Anatomy and Physiology16th EditionCharles Welsh, Cynthia Prentice-Craver, David Shier, Jackie Butler, Ricki Lewis 727 solutions
Essentials of Anatomy and Physiology6th EditionEdwin F. Bartholomew, Frederic H. Martini 1,271 solutions
Human Anatomy and Physiology Laboratory Manual12th EditionElaine N. Marieb, Lori A. Smith 1,786 solutions Recommended textbook solutions
Hole's Human Anatomy and Physiology13th EditionDavid N. Shier, Jackie L. Butler, Ricki Lewis 1,402 solutions
Hole's Human Anatomy and Physiology15th EditionDavid Shier, Jackie Butler, Ricki Lewis 1,950 solutions
Mader's Understanding Human Anatomy and Physiology10th EditionSusannah Longenbaker 1,332 solutions
Essentials of Anatomy and Physiology2nd EditionKenneth Saladin, Robin McFarland 1,940 solutions BIO 301Human Physiology Respiration Respiratory System:
Respiratory system The exchange of gases (O2 & CO2) between the alveoli & the blood occurs by simple diffusion: O2 diffusing from the alveoli into the blood & CO2 from the blood into the alveoli. Diffusion requires a concentration gradient. So, the concentration (or pressure) of O2 in the alveoli must be kept at a higher level than in the blood & the concentration (or pressure) of CO2 in the alveoli must be kept at a lower lever than in the blood. We do this, of course, by breathing - continuously bringing fresh air (with lots of O2 & little CO2) into the lungs & the alveoli. Breathing is an active process - requiring the contraction of skeletal muscles. The primary muscles of respiration include the external intercostal muscles (located between the ribs) and the diaphragm (a sheet of muscle located between the thoracic & abdominal cavities). The external intercostals plus the diaphragm contract to bring about inspiration:
To exhale:
Intra-alveolar pressure during inspiration & expiration As the external intercostals & diaphragm contract, the lungs expand. The expansion of the lungs causes the pressure in the lungs (and alveoli) to become slightly negative relative to atmospheric pressure. As a result, air moves from an area of higher pressure (the air) to an area of lower pressure (our lungs & alveoli). During expiration, the respiration muscles relax & lung volume descreases. This causes pressure in the lungs (and alveoli) to become slight positive relative to atmospheric pressure. As a result, air leaves the lungs (check this animation by McGraw-Hill). The walls of alveoli are coated with a thin film of water & this creates a potential problem. Water molecules, including those on the alveolar walls, are more attracted to each other than to air, and this attraction creates a force called surface tension. This surface tension increases as water molecules come closer together, which is what happens when we exhale & our alveoli become smaller (like air leaving a balloon). Potentially, surface tension could cause alveoli to collapse and, in addition, would make it more difficult to 're-expand' the alveoli (when you inhaled). Both of these would represent serious problems: if alveoli collapsed they would contain no air & no oxygen to diffuse into the blood &, if 're-expansion' was more difficult, inhalation would be very, very difficult if not impossible. Fortunately, our alveoli do not collapse & inhalation is relatively easy because the lungs produce a substance called surfactant that reduces surface tension. Role of Pulmonary Surfactant
Lung cells that produce surfactant Exchange of gases:
Partial Pressures of O2 and CO2in the body (normal, resting conditions): (check this animation by McGraw-Hill)
While in the alveolar capillaries, the diffusion of gasses occurs: oxygen diffuses from the alveoli into the blood & carbon dioxide from the blood into the alveoli.
How are oxygen & carbon dioxide transported in the blood?
2 - dissolved in the plasma (1.5%) Because almost all oxygen in the blood is transported by hemoglobin, the relationship between the concentration (partial pressure) of oxygen and hemoglobin saturation (the % of hemoglobin molecules carrying oxygen) is an important one. Hemoglobin saturation:
The relationship between oxygen levels and hemoglobin saturation is indicated by the oxygen-hemoglobin dissociation (saturation) curve (in the graph above). You can see that at high partial pressures of O2 (above about 40 mm Hg), hemoglobin saturation remains rather high (typically about 75 - 80%). This rather flat section of the oxygen-hemoglobin dissociation curve is called the 'plateau.' Recall that 40 mm Hg is the typical partial pressure of oxygen in the cells of the body. Examination of the oxygen-hemoglobin dissociation curve reveals that, under resting conditions, only about 20 - 25% of hemoglobin molecules give up oxygen in the systemic capillaries. This is significant (in other words, the 'plateau' is significant) because it means that you have a substantial reserve of oxygen. In other words, if you become more active, & your cells need more oxygen, the blood (hemoglobin molecules) has lots of oxygen to provide When you do become more active, partial pressures of oxygen in your (active) cells may drop well below 40 mm Hg. A look at the oxygen-hemoglobin dissociation curve reveals that as oxygen levels decline, hemoglobin saturation also declines - and declines precipitously. This means that the blood (hemoglobin) 'unloads' lots of oxygen to active cells - cells that, of course, need more oxygen.
The oxygen-hemoglobin dissociation curve 'shifts' under certain conditions. These factors can cause such a shift:
CO2 + H20 -----> H2CO3 -----> HCO3- + H+ & more hydrogen ions = a lower (more acidic) pH. So, in active tissues, there are higher levels of CO2, a lower pH, and higher temperatures. In addition, at lower PO2 levels, red blood cells increase production of a substance called 2,3-diphosphoglycerate. These changing conditions (more CO2, lower pH, higher temperature, & more 2,3-diphosphoglycerate) in active tissues cause an alteration in the structure of hemoglobin, which, in turn, causes hemoglobin to give up its oxygen. In other words, in active tissues, more hemoglobin molecules give up their oxygen. Another way of saying this is that the oxygen-hemoglobin dissociation curve 'shifts to the right' (as shown with the light blue curve in the graph below). This means that at a given partial pressure of oxygen, the percent saturation for hemoglobin with be lower. For example, in the graph below, extrapolate up to the 'normal' curve (green curve) from a PO2 of 40, then over, & the hemoglobin saturation is about 75%. Then, extrapolate up to the 'right-shifted' (light blue) curve from a PO2 of 40, then over, & the hemoglobin saturation is about 60%. So, a 'shift to the right' in the oxygen-hemoglobin dissociation curve (shown above) means that more oxygen is being released by hemoglobin - just what's needed by the cells in an active tissue! Carbon dioxide - transported from the body cells back to the lungs as:
Control of Respiration Your respiratory rate changes. When active, for example, your respiratory rate goes up; when less active, or sleeping, the rate goes down. Also, even though the respiratory muscles are voluntary, you can't consciously control them when you're sleeping. So, how is respiratory rate altered & how is respiration controlled when you're not consciously thinking about respiration? The rhythmicity center of the medulla:
Pneumotaxic center (also located in the pons) - inhibits apneustic center & inhibits inspiration Factors involved in increasing respiratory rate
Heavy exercise ==> greatly increases respiratory rate Mechanism?
Related links: The Respiratory System Introduction to Anatomy: Respiratory System Back to BIO 301 syllabus Lecture Notes 1 - Cell Structure & Metabolism Lecture Notes 2 - Neurons & the Nervous System I Lecture Notes 2b - Neurons & the Nervous System II Lecture Notes 3 - Muscle Lecture Notes 4 - Blood & Body Defenses I Lecture Notes 4b - Blood & Body Defenses II Lecture Notes 5 - Cardiovascular System What is the correct order of structures that air passes through?When you inhale through your nose or mouth, air travels down your pharynx (back of your throat), passes through your larynx (voice box) and into your trachea (windpipe). Your trachea is divided into two air passages called bronchial tubes. One bronchial tube leads to your left lung, the other to your right lung.
What is the correct order of air flow during an inspiration?The process of taking air into the lungs is known as inspiration or inhalation, and the process of breathing it out is expiration or exhalation. Air is inhaled through the mouth or through the nose. The sequence of air passage during inhalation is as follows: Nostrils→pharynx→larynx→trachea→alveoli.
Which of the following lists the order of structures through which air will pass during inspiration group of answer choices?Final answer: The correct sequence of air passage during inhalation is Nostrils→ pharynx → larynx→ trachea→ alveoli.
What is the order of structures air passes through on its way to the alveoli?On its way to the alveoli of the lungs air travels through the nasal cavity, pharynx, larynx, trachea, bronchi and bronchioles.
|